Improvement in pistons



OFFICE.

cHAnLES n. ALLEN, or PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT |N PlsToNs.

Specification forming part of Letters Patent No. 142,659, dated September 9, 1873; application filed July 19, 1873.

To all whom it may concern:

Be it known that I, CHARLES B. `ALLEN, of Philadelphia, Pennsylvania, have invented certain Improvements in Pistons, of which the following is a specification:

The object of my invention is to improve that class of pistons in which the packingrings are expanded by the operation of cams; and this object I attain by simplifying the construction of pistons of this class in the manner which I will proceed to explain, reference being had to the accompanying drawing, in which- Figure l represents a plan view of my improved piston with the cover removed, and Fig. 2 a vertical section of the piston.

The body of the piston consists of a central hub, a, the plate or flange d, and a number of arms or ribs, e, (three in the present instance,) radiating from the hub, the whole being as usual cast in one piece. The end of the pistonrod bis fitted int-o and secured 'to the central hub in the ordinary manner, and to the ribs is fitted and secured the usual cover f, between which and the flange or plated intervene split packing-rings h h of the usual construction. To a circular projection, c', forming part of the central hub of the piston,'and concentric with the same, is so iitted a ring, B, that it can be turned freely, the ribs c being recessed to receive the ring, Vthe outer surface of which is in the same plane as the upper edges of the ribs, so that it may be effectually confined to its place by the cover f. In this ring B there are vthree eccentric slots, each of which receives a projection, n, on a pin, D, the outer end of which enters an orice in-a segmental block, E, the outer rounded surface of the latter coinciding with and abutting against the inner Surface of the packing-rings.

On turning the ring B in the direction of the arrow, which can be accomplished after the removal of the cover f, all the pins D will be simultaneously moved outward, and the packing-rings will, consequently, be expanded with a yielding pressure, for a sprin g coiled round each pin intervenes between a collar on the pin and the block D, and is the medium through which the force to expand -the rings is exerted.

It' desired, however, the springs may be dispensed with, and the pins caused to bear directly against the blocks D.

It is important that the pins should be main tained steadily in their places, in order that they may properly receive the action of the eccentric slots in the ring B. With this object in view each pin is guided at the rear by its projection p entering an orifice of the hub a, and is further vguided and prevented from turning by its projection q entering a slot, q', formed by two ribs, t t, cast on the body ot' the piston at the junction of the hub with the plate d. (See detached view, Fig. 3.) In one of the ribs e is a recess for receivn g the butt of the pawl H, one of the screws for securing the cover passing through the pawl, the outer end of which is adapted to ratchetteeth on the edge of the ring B, thereby retaining the latter in any position to which it may have been turned, the pawl possessing within itself sufficient elasticity to render a sprin g unnecessary.

It will be seen without further description that the disposition of the parts composing the above-described piston is of `the most simple character; that care has been taken to avoid complication and expensive tting; that all the parts are easily accessible; and that the adjustments are positive, and such as to insure perfect centering of the rings.

I claim as my invention- 1. The ring B, having eccentric slots m, in combination with guided pins D, projections of which extend into the said slots, substantially as and for the purpose set forth.

2. The pin D, guided at the rear in the hub of the piston, and at the front in the block F, and having a projection, n, adapted to one of the curved slots in the ring B, and the projection q guided by ribs t t, all as specified.

3. The pawl H, fitted to a recess in one ot' `the ribs c of the piston, and adapted to ratchet-teeth on the ring B, all as described. In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses. GHAS. B. ALLEN.

Witnesses:

WM. A. STEEL, HARRY SMITH. 

